Flotation machine and stator therefor



June 27, c M ANDERSON FLOTATION MACHINE AND STATOR THEREFOR Filed Jan. 25, 1965 IIIII" II I II III." IIIIIIIIIIILWIIIIIIIIIIII INVEN TOR. M. ANDERSON CHARLES ATTORNEYS United States Patent 3,327,851 FLOTATION MACHINE AND STATOR THEREFOR Charles M. Anderson, Salt Lake City, Utah, assignor to The Galigher Company, Salt Lake City, Utah, a corporation of Utah Filed Jan. 25, 1965, Ser. No. 427,639 Claims. (Cl. 209-169) This invention relates to the type of sub-aeration flotation machine shown in US. Patents Nos. 2,055,065 and 2,182,442 granted to Lionel E. Booth under dates of Sept. 22, 1936, and Dec. 5, 1939, respectively, and also shown in improved form in US. Patents Nos. 2,673,724 and 2,767,964 granted to John T. Potts under dates of Mar. 30, 1954, and Oct. 23, 1956, respectively. This type of machine has long been manufactured by The Galigher Company of Salt Lake City, Utah, and is well known in the flotation art.

Flotation machines of this type are characterized by the combination of an aerating impeller, having a multiplicity of closely spaced fingers depending from the rim of an essentially closed top member, which is usually of disk formation as shown in the aforementioned Potts patents, and a concentric stator structure, comprising a multiplicity of mutually spaced blades or vanes extending radially of the impeller and circumferentially surrounding it. This mechanism is mounted near the bottom of a square tank adapted to contain metallurgical pulp and to form one cell in a series of such cells through which the pulp flows from one end of the series to the other.

The blades of the stator, or bubble peeler as it is sometimes called, have extended radially outwardly from the impeller to or almost to the Walls of the flotation tank, and, therefore, have been of widely difiering lengths, depending upon whether they are disposed at the corners of the tank or intermediate the corners.

In accordance with the present invention, the stator blades are shortened considerably in their outward extension from the impeller and are all of the same or substantially the same length, to provide a ring closely encircling the impeller. They are mounted on and rise from a square bottom plate, which is spaced upwardly from the bottom of the tank and extends almost to the walls thereof to positively direct the pulp to the outer reaches of the tank for recirculation around and below such bottom plate. It has been found that the shorter blades satisfactorily stabilize and direct the circulating pulp and that the relatively greater speed of pulp flow which is thereby insured and the greater unrestricted area below the bubble column which is thereby attained make for significantly improved operation.

There is shown in the accompanying drawings a specific embodiment of the invention representing what is presently regarded as the best mode of applying it in actual practice. From the detailed description of this illustrated form, various specific objects and features of the invention will become apparent.

In the drawings:

FIG. 1 represents a central vertical section taken through a flotation cell conforming to the invention, the impeller and drive assembly therefor being shown in elevation;

FIG. 2, a horizontal section taken along the line 22 of FIG. 1 and leaving out exterior structural details;

FIG. 3, a similar horizontal section taken along the line 33 of FIG. 1;

FIG. 4, a fragmentary vertical section taken along the line 44 of FIG. 2;

FIGS. 5 and 6, enlarged, fragmentary, schematic views in central vertical section showing, respectively, the pres ent improvement in contrast to the prior construction,

ice

particularly as concerns pulp recirculation, which is indicated by appended arrows.

Referring to the drawings:

The illustrated flotation machine is typical of the type previously referred to, being provided with a square flotation tank 12 having the usual provision for pulp inflow and for tailings outflow (not shown) and the usual froth overflow lips. The customary aerating impeller 14 is mounted at the lower end of the usual hollow impeller shaft 15 for rotation by the conventional power drive arrangement indicated generally by the reference number The impeller 14 is conventional and comprises a closed top member 14a of flat disk formation and a circumferential series of closely spaced fingers 14b depending from the rim of top member 14a. Air entering the impeller from shaft 15 mixes with pulp entering from the open bottom of the impeller, and the mixture is discharged laterally through the multiplicity of side-discharge ports 140, FIG. 3, formed by the circumferential series of spaces between the depending fingers of the impeller.

The unique stator or peller blade structure which characterizes this new flotation machine comprises, in the illustrated embodiment, a multiplicity of mutually spaced blades 17 radiating outwardly from and defining a circular space 18, FIG. 2, for the reception of impeller 14. The blades 17 are interconnected by and rise from rigid securement, as by welding, to the upper surface of a bottom plate 19, configurated to conform generally with the horizontal cross-sectional configuration of the interior of tank 10 but being somewhat smaller so as to provide peripheral, pulp-recirculation passages 20 between the outer edges of such bottom plate and the side walls of the tank when the stator is installed in the tank.

The stator is spaced above the bottom of tank 10 by sets of feet 21 and 22, respectively, FIGS. 2 and 4, so bottom plate 19 thereof is raised sufliciently above the bottom of the tank to provide a bottom, recirculation space or passage 23. The feet 21 are fastened to and rise from the bottom of the tank, as by welding, and have seats 21a for receiving notched corners of the stator plate 19, so that such plate rests freely thereon. The feet 22 are fastened to and depend from the underside of stator plate 19 peripherally of the inner circumferential edge thereof which defines impeller-receiving space 18. They rest freely on the bottom of the tank. Thus, the entire stator unit can be easily lifted out of the tank for repair or replacement.

As illustrated, the basic steel structure is faced with wear-resistant rubber of the like in customary manner wherever exposed to abrasive action of the pulp.

The stator blades 17, as previously mentioned, are shorter than the corresponding blades of the conventional stator and are of substantially equal length to provide an annulus, which closely encircles impeller-receiving space 18 and presents a circumferential series of stator passages 24 confronting the side-discharge ports 14c. Stator bottom plate 19 extends from the inner ends of such blades, substantially at space 18, to short of the peripheral walls of the tank in order to define the pulp-recirculation passages 20. Blades 17 are substantially no longer than about one-half the widths of the narrowest portions of the plate 19 lying between opening 18 and the outer periphery of such plate, so as to properly stabilize the aerated pulp discharged by the impeller, without reducing its velocity any more than can be avoided.

As indicated by the appended arrows in FIGS. 5 and 6, respectively, circulation of pulp in the arrangement of the invention is completely through the stator passages 24 and on out over the unencumbered outer margins of stator bottom plate 19, downwardly through peripheral pulp-recirculation passages 20, and back to the impeller through bottom space or passage 23, While, in the conventional arrangement, circulation tends to be localized within a relatively short circuit largely within the confines of the usual stator plates 25, FIG. 6.

Comparative tests between these arrangements have shown that of the invention to be significantly superior. Thus, in typical examples, Where the tests were carried out under identical conditions on a metallurgical pulp with the following screen analysis:

Screen size: Percent of total Total 100.0

the following results were obtained:

EXAMPLE I.-60" CELL PERFORMANCE COMPARISON Solids to Surface, Percent Average Max. Sanding in Corners, Inches Feet per Minute Peripheral Speed Plate Type Std. Plate Type Std.

Stator Stator Stator Stator EXAMPLE 11-48" CELL PERFORMANCE COMPARISON Solids to Surface, Percent Average Max. Sanding in Corners, Inches Feet per Minute Peripheral Speed Plate Type Std. Plate Type Std.

Stator Stator Stator Stator flotation tank having a bottom and peripheral walls; an

impeller rotatably mounted in the tank adjacent to but spaced above the bottom thereof, said impeller having a top member of substantially closed, circular formation,

and a multiplicity of closely spaced fingers depending from the rim of the top member in mutually spaced relationship to define a plurality of side-discharge ports, the bottom of the impeller being substantially entirely open; and a stator in the form of peeler blade structure made up of a multiplicity of mutually spaced blades spaced above the bottom of the tank and radiating outwardly from and defining a circular space within which the impeller is mounted for rotation on a vertical axis concentric with the axis of the stator, the improvement comprising:

a bottom plate for the stator spaced above the bottom Wall of the tank and having an opening therethrough substantially concentric with said circular space, said bottom plate extending short of the peripheral walls of the tank by enough space to provide for pulp circulation from above to below the plate;

the said blades being fixed in position on said plate and being substantially uniform in length and extending outwardly substantially no more than about one-half the width of the plate at any point between the impeller and the outer periphery of said plate and, collectively, defining a relatively narrowwalled annulus closely surrounding the impeller.

2. The improvement defined by claim 1, wherein the bottom plate of the stator is secured to the bottom edges of the stator blades as an integral part of the stator assembly.

3. The improvement defined by claim 2, wherein the stator assembly is freely supported on the bottom of the tank.

4. The improvement defined by claim 1, wherein the 5 tank is square and the bottom plate of the stator is square.

5. A flotation machine stator, comprising a multiplicity of mutually spaced stator blades radiating outwardly from and defining a circular space for the reception of a flotation impeller; a bottom plate having an opening therethrough substantially concentric with said circular space, said blades being fixedly secured to said plate and being substantially uniform in length and extending outwardly substantially no more than about one-half the width of the plate at any point between said space and the outer periphery of the bottom plate and, collectively, defining a relatively narrow-walled annulus closely surrounding said space; and means for supporting said bottom plate above the bottom of a flotation tank.

References Cited UNITED STATES PATENTS 2,198,143 4/1940 Weinig 26l-87 2 ,767,964 10/1956 Potts 20 9-469 X 2,875,897 3/1959 Booth 26187 X HARRY B. THORNTON, Prima/y Examiner.

L. EATHERTON, Assistant Examiner. 

5. A FLOTATION MACHINE STATOR, COMPRISING A MULTIPLICITY OF MUTUALLY SPACED STATOR BLADES RADIATING OUTWARDLY FROM AND DEFINING A CIRCULAR SPACE FOR THE RECEPTION OF A FLOTATION IMPELLER; A BOTTOM PLATE HAVING AN OPENING THERETHROUGH SUBSTANTIALLY CONCENTRIC WITH SAID CIRCULAR SPACE, SAID BLADES BEING FIXEDLY SECURED TO SAID PLATE AND BEING SUBSTANTIALLY UNIFORM IN LENGTH AND EXTENDING OUTWARDLY SUBSTANTIALLY NO MORE THAN ABOUT ONE-HALF THE WIDTH OF THE PLATE AT ANY POINT BETWEEN SAID SPACE AND THE OUTER PERIPHERY OF THE BOTTOM PLATE AND, COLLECTIVELY, DEFINING A RELATIVELY NARROW-WALLED ANNULUS CLOSELY SURROUNDING SAID SPACE; AND MEANS FOR SUPPORTING SAID BOTTOM PLATE ABOVE THE BOTTOM OF A FLOTATION TANK. 